Infinity scarves are really popular right now and for good reason. They keep you warm and you can wrap them around a bunch of times, without having to worry about the ends being blown away in a windstorm or tying yourself in a knot. If you would like to knit an infinity scarf, first you need to know how to knit in the round. So here is a short needle and if I were making an infinity scarf out of this sort of a needle, I would be getting a circumference actually closer to a cowl, which is just a really short infinity scarf that is worn around the neck.
So what you would do is you would be knitting in the round, but you would be using a really long circular needle. You can get ones even longer than this. So you're going to cast on and join to knit in the round, and then knit around and around and around and around, in whatever stitch pattern you fancy or whatever the pattern calls for until you've got your desired height and then you would cast off, making essentially a super-wide cowl or an infinity scarf that you can wrap around a couple times and never have to tie. So good luck making your infinity scarf as big as you want.